Seismic analysis of the active character of the Taihang Mountain piedmont fault

The Taihang Mountain piedmont fault is a large-scale structure zone in north and east China which cross Beijing,with the NE-NNE extent spans approximately 620 km.It is very important to determine the fault zone activity due to the close relation of active structures and earthquakes.Regarding the fault activity,there are three different opinions：1） it is a large deep fault zone;2） it is an active fault zone and an earthquake structure belt;and 3） it is not an earthquake structure belt.In order to ascertain the active character of the fault,the deep tectonic setting and the activity since the Quaternary were investigated using recent seismic and drilling data to make a joint interpretation.The investigation results show that the Taihang Mountain piedmont fault is not a large lithospheric fault because the early middle Pleistocene（Q（P2）） layers are offset by the fault and the late middle Pleistocene（Q（P2）） and late Pleistocene layers are not offset by the fault.We determine that the Taihang Mountain piedmont fault in the area is not an active fault and is also not a large lithospheric fault.This study result provides important geological and geophysical data for city planning and construction in Hebei province and, especially,has great significance for seismic hazard assessment of the capital area.

Hurricane disturbances, tree diversity, and succession in North Carolina Piedmont forests, USA

Windthrow plays a critical role in maintaining species diversity in temperate forests. Do large-scale strong wind events(i.e., tropical cyclones, including hurricanes,typhoons and severe cyclonic storms) increase tree diversity in severely damaged forest areas? Do hurricanes(tropical cyclones that occurs in the Atlantic Ocean and northeastern Pacific Ocean) lead to altered relative abundance of shade-tolerant and shade-intolerant species? Did historic hurricanes alter the succession trajectory of the damaged forests? We used nearly 70-year tree demographic data to assess the effects of two major hurricanes on woody species diversity in Piedmont forests, North Carolina, USA. Species richness(S) and Shannon–Wiener's diversity index(H') were used to evaluate the changes in tree diversity. The changes in composition were assessed with Nonmetric Multidimensional Scaling. The pre-hurricane successional phase can strongly influence both the damage severity and subsequent responses. Although there is often an immediate drop in diversity following a hurricane, understory tree diversity quickly increases to levels that exceed those prior to the disturbance. This leads to an increase in diversity in stands that were substantially damaged. Hurricanes significantly decrease the dominance of shade-intolerant canopy species while increasing preestablished, more shade-tolerant species. We conclude that large, and infrequent hurricanes help to maintain local tree diversity, but also accelerate the increase in dominance of understory species such as red maple and beech.

Late Pleistocene-Holocene slip history of the Langshan-Seertengshan piedmont fault(Inner Mongolia,northern China) from cosmogenic ^(10)Be dating on a bedrock fault scarp

Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault （LSPF）, one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ^10Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 Ira and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 ±0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.

Late Quaternary Activity of the Huashan Piedmont Fault and Associated Hazards in the Southeastern Weihe Graben,Central China

The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.

Assessment of Groundwater Source of Piedmont Plain Area of China Northwest Arid Region Based On Numerical Modeling

After the middle of 1960s,along with the appearance and extensive utilization of computer featured in large capacity and rapid speed,numerical method(mainly include finite difference method and finite element

Experimental study on unsaturated soil water diffusivity in different soils in Hebei Piedmont Plain

Horizontal soil column method was used to determine the horizontal diffusion rate of sandy loam, loam and clay loam under the same bulk density. The results showed that the migration rates of different lithological wet fronts were different. The sandy loam had the fastest migration rate, the loam followed, and the clay loam was the slowest, but the law of change is the same among the three lithologies. The volumetric water content affects the change of Boltzmann parameter λ. When the volumetric water content is between 0.35-0.45 cm^3/cm^3,λ approaches stability. When the volumetric water content is less than 0.35 cm^3/cm^3, the λ value decreases rapidly with the decrease of water content. The water diffusion rate is related to the volumetric water content and particle size. The greater the moisture content is, the greater the diffusion rate will be. The larger the particle size, the larger the diffusion rate. The diffusivity of sandy loam is 10-30 times larger than that of loam and clay loam. The relationship between water content and diffusion rate is in accordance with the exponential function .

Analysis on Long Precipitation Series in Piedmont (North-West Italy)

This study analyses thirteen daily precipitation series of Piedmont, region of North-West Italy. The meteorological series have been chosen because they were meteorological observatories operating continuously from the beginning of 1900 until 2011. As the first step an historical research over each station has been carried out. In this way, the potential breaks, in the series, either due to changes of locations or instruments, have been determined and the missing values have been recovered. On the precipitation daily series a quality control have been effectuated and by metadata identification it was possible to assess the homogeneity of the meteorological series. In this way we have obtained the complete and correct series on which trends have been computed. In order to better understand the consequences of climate variations on our environment and society, we have calculated the climate indices proposed by “CCL/CLIVAR Working Group on Climate Change Detection” (dry and wet days, rainy days, intensity of precipitation…) over the time. The values of precipitation have also allowed beginning the climatic analysis with the aim at defining the principle local peculiarity in Piedmont.

History of Paleoseismic ActivityAlong the Hohhot Segment of Daqingshan Piedmont Fault in the Late Quaternary

A detailed study on geomorphic surfaces and a set of trenches on the Hohhot segment of Daqingshan piedmont fault at three sites, Kuisu, Ulan Blang, and Qingshan Grassland, revealed 7 paleoseismic events occurred along the fault segment since 19 ka BP. Those events occurred at 18.75±.75 ka, 16.97 ±.96 ka, 14.65±.67 ka, 11.82±.69 ka, 9.45±.26 ka, 6. 83±.26 ka, and 4. 50 ±0. 23 ka BP, respectively, and their average recurrence interval is 2375±432 years. From the results of constraining fault displacement and correlation between the sediments in these trenches, we found a complete paleoseismic activity history along the fault segment during this period of time.

Paleoseismic activity on Wujiahe segment of Serteng piedmont fault, Inner Mongolia

Geomorphic study on Wujiahe segment of Serteng piedmont fault, Inner Mongolia is made. Through analysis of the available data in combination with the results of predecessors studies it can be obtained that average vertical displacement rate is 0.48~0.75 mm/a along the Wujiahe segment since the late Pleistocene (14.450~22.340 ka BP) and 0.56~0.88 mm/a since the early-middle Holocene (5.570~8.830 ka BP). Analyzing paleoseismic phenomena revealed in the excavated 5 trenches in combination with the results of predecessors studies of paleoearthquakes on the fault, we determine five paleoseismic events on the Wujiahe segment of Serteng piedmont fault since 27.0 ka BP and the recurrence interval to be about 4.300~4.400 ka. A cluster of paleoearthquakes occurred probably during 8.000~9.000 ka BP and two paleoseismic events in 10.000~20.000 ka BP may be missed. A comparison between height of fault scarps and sum of displacement caused by paleoseismic events revealed in trenches, and recurrence interval of paleoseismic events obtained from average displacement rate along the fault and the disloca-tion by one event suggest that three paleoseismic events are absent in Alagaitu trench. Two paleoseismic events may be absent on the whole active fault segment.

Active Northern Huashan Piedmont Fault Zone and Geological Hazard in Shaanxi Province

On the basis of field observation and measuring data, the authors discuss the types,distributing regularity and gemesos of geological disasters on the Northern Huashan predmont and its foreland plain. We think that the activity of Northern Huashan piedmont fault zone since Quaternary period makes the mountain highly uplift,which provide a favorable terrain condition for gravitatiotal geological hazard;the recent activity of the buried fault on the foreland plain is the main reason of ground cracking and sinking .Finally ,we make a synthetical analysis of geological hazard risk on the study area.

The Research of the Activity of the Piedmont Fault on the Tangshankou Segment of the Yuguang Basin Southern Marginal Fault

The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9 ka for the first time,and then faulted again at about 7. 3 ka,causing the formation and synchronous activity of another fault.Finally,they faulted for the third time,but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8. 1 m. We estimate that the average recurrence period of the piedmont fault is about 1. 7 ka,and the average slip rate of the piedmont fault is about1. 6 mm/a. We also estimate the reference magnitude of each event according to the empirical formula.

Sinistral Strike-slip Movement Along Western Terminal Segment of the Active Daqingshan Piedmont Fault, Inner Mongolia, China

There are 18 gullies displaying sinistral contortions to different degrees along the western terminal segment about 10 km long of the active Daqingshan piedmont fault near the Donghe District, Baotou City. The contortion amount of gullies ranges from 20 m to 300 m. The contortion and length of the gullies are in direct proportion. The relation between piedmont terraces and gullies indicates that the gullies with upper reaches of about 1 ～ 5 km long and those smaller than one kilometer were formed at the end of Late Pleistocene and Holocene.Meanwhile, sandy gravel layer of alluvial-proluvial sediment on the upthrown wall is directly in contact with yellow clayey sand of the downthrown wall. During the Holocene, the sinistral strike-slip rate along the western terminal segment of the active Daqingshan piedmont fault reached 5 mm/a from age data of dislocated sediments. The evolutional mechanism of the active Daqingshan piedmont fault is also discussed in the paper.

Holocene Paleoseismic Activity Along the Northern Piedmont Fault of the Hengshan Mountain, South of Datong Basin in Shanxi Province

Our field investigation indicates that the northern piedmont fault of the Hengshan Mountain has dislocated proluvial fan and terrace I of the gully mouth on the northern border of the Hengshan Mountain. Stratigraphic age data indicates that the surface layer in the middle and rear part of the proluvial fan and on the terrace I of the gully mouth on the mountain border consists of sediments of about 5200～6800a B.P. The Hezhuang and Niucaoyu trenches excavated in the front of Hengshan Mountain revealed that 3 paleoseismic events have occurred along the northern piedmont fault of Hengshan Mountain since the early Holocene. The 3 paleoseismic events occurred in 2260±190～4370±150a BP, nearly 5628±150a BP, and 8083±250～8430±720a BP, respectively, and their recurrence interval is 2313a,2628a and 2471a on average. The coseismic vertical displacement produced by these events is 1 0～3 0m. The elapsed time of the latest movement along the fault has exceeded the recurrence interval of these paleoearthquakes. Thus, there exists the possibility of strong earthquake occurrence along the fault from now onward, so the fault is in need of observation.

Investigation of Terraces along the Luoyunshan Piedmont Fault Zone and Its Tectonic Implications

Located at the west of the Linfen basin, the Luoyunshan piedmont fault zone controls the western boundary of the basin. According to the measurements of the terraces in eight gullies along the Luoyunshan fault zone, five levels of terraces, namely T1～T5 have developed in these gullies. The heights of terraces T1, T2, T3, T4 and T5 are about 3m, 8～10m, about 20m, about 30m and 40～50m, respectively. The dating data of the terraces and investigation of the faulted landforms show that the Luoyunshan fault zone has experienced much activity since the Late Quaternary. The uplift rate of the terraces was 0.41mm/a since the Middle-Late Pleistocene, and 0.75mm/a since the Holocene. The increasing trend of uplift rate of the terraces along the Luoyunshan fault zone from the Middle-Late Pleistocene to Holocene indicates the tendency of gradual tectonic uplift of the fault zone since the late Quaternary. This is in good agreement with the increasing trend of subsidence rate of the Linfen basin from the Late Pleistocene to Holocene.

Late-Quaternary Movement Along the Sertengshan Piedmont Fault and a Model for Segmentation of Its Rupture

Analysis and study of the geometrical structure of the fault, tectonic features of late Quaternary movement, paleoseismic activity, and structural characteristics of boundaries between segments of the Sertengshan piedmont fault permitted us to preliminarily determine the following 4 active segments of the fault: the Wujiahe segment (from Dongwugai Gully to Dahoudian Village), Wujumengkou Dongfeng Village segment (from Dahoudian to Delingshan), Dashetai segment (from Delingshan to Xiaoshetai Gully mouth), and the Ulan Hudong segment (from Xiaoshetai Gully mouth to Tailiang). The boundaries between them are the Dagoudian mountain spur, the Delingshan Mountain spur and the step zone at Xiaoshetai Gully mouth, respectively. The segments are independent for seismic activity. However, it is possible that joint ruptures between Wujiahe and Wujumengkou Dongfeng Village segments and between Dashetai and Ulan Hudong segments may occur.

Late Quaternary Activity and Paleoearthquakes along the Nanyukou Segment of the Northern Piedmont Fault of Wutai Mountain

The northern piedmont fault of Wutai Mountain is located at the north of the Shanxi Graben system, which is the dominating fault of the south boundary of the Fanshi-Daixian depression. This paper discusses the fault activity and paleoearthquakes around the Nanyukou segment of the northern piedmont fault of Wutai Mountain during the late Quaternary through field investigation along the fault, measuring geomorphic deformation and excavating trenches at some important sites. From Nanyukou to the southwest of Shanhui, we find obviously dislocated alluvial fans, with strong neotectonic movement at these sites. Since nearly 20ka, the vertical average slip rate is 1.55mm/a to 2.0mm/a. However,since nearly 6ka,it has reached as high as 2.3mm/a, which is twice that on other segments. 2 trenches were excavated around Nanyukou with 6 events discovered. The referenced ages of the events are before 7600a, 6700a - 7600a, 5321a - 5575a, 4400a - 5400a,420Oa-4400a and after 1600a B.P. with approximate recurrence interval 1400a. The latest event is likely to be the earthquake occurring at 512 A. D. ,so it is necessary to do further work to verify this in the future.

Late Quaternary Activity of the Central-North Segment of the Taihang Mountains Piedmont Fault Zone

The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.

天山北坡前山带12种植物对干旱胁迫和复水的生理响应及抗旱性评价

【目的】前山带是天山北坡山地-绿洲-荒漠生态系统的重要组成部分,探讨植物对干旱胁迫的动态生理适应性和抗旱性评价方法,筛选植被恢复的适宜树种,对该区域植被生态恢复具有重要意义。【方法】以新疆天山北坡前山带种植的12种植物为研究对象,观测灌水后土壤水分时空变化,分析干旱和复水对植物光合和抗逆生理指标的影响,采用主成分分析评价12种植物的抗旱能力。【结果】(1)干旱胁迫后,土壤水分散失在0-20 cm层最快,20-40 cm层次之,40-60 cm层最慢,不同植物采用不同策略改变生长情况来适应干旱;(2)干旱胁迫后,叶片净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(T_(r))、胞间CO_(2)浓度(C_(i))、PSⅡ潜在活性(F_(v)/F_(o))、PSⅡ最大光化学效率(F_(v)/F_(m))、电子传递速率(ETR)和叶绿素含量降低,而抗逆生理指标超氧化物歧化酶(SOD)活性、脯氨酸含量、丙二醛(MDA)含量及非光化学淬灭系数(qN)升高,复水后各指标都有一定程度的恢复,但均未达到初始水平;(3)主成分分析结果显示,Pn、叶绿素含量、ETR和MDA含量等指标贡献率较大,梭梭、柽柳、刺蔷薇和柠条锦鸡儿抗旱性较强,‘中亚沙棘’、‘新棘5号’、‘新棘1号’和山杏次之,而‘新棘4号’、‘新棘3号’、文冠果和‘新棘2号’较弱。【结论】Pn、叶绿素含量、ETR和MDA含量可作为评价植物适应干旱的重要指标;新疆天山北坡前山带植被生态恢复应优先选择梭梭、柽柳、刺蔷薇及柠条锦鸡儿进行建植。

邯郸山前平原地下水流场演变及其驱动力

20世纪60年代初邯郸山前平原浅层地下水位大幅下降,地下水降落漏斗逐渐形成,地下水流场剧烈演变,采用时间序列分析、相关分析、水均衡等方法,分析了邯郸山前平原浅层地下水流场的演变规律及其驱动力,并计算了1981—2019年各影响因素对地下水流场演变的贡献率,结果表明:1960年以前邯郸山前平原浅层地下水流场演变主要受自然因素驱动,1960年以后地下水流场演变的驱动力由自然因素演化为人为因素和自然因素,地下水源汇项逐渐发生变化;邯郸山前平原排泄项对地下水流场演变的贡献率大于补给项,降水入渗和地下水开采始终是浅层地下水流场演变的主要驱动力;1981—2000年降水入渗补给量和开采量对浅层地下水流场演变的贡献率为80.82%,2001—2019年降水入渗补给量和开采量对浅层地下水流场演变的贡献率为75.79%,浅层地下水流场演变的驱动力趋于多元化。

塔西南山前地区柯克亚周缘叶探1井油气勘探重大突破及意义

塔西南山前西昆仑冲断带柯东构造带叶探1井在二叠系普斯格组获得重大突破,标志着塔西南山前地区发现一个重要的勘探接替层系。结合区域地质资料,根据野外露头、钻井、地震等综合研究,对柯克亚周缘二叠系普斯格组的成藏条件进行再认识。研究认为,研究区内二叠系普斯格组发育陆相湖泊—三角洲沉积体系,上段发育半深湖—深湖相烃源岩,面积1.0×10^(4)km^(2),厚度最大达到800m,集中段有机质丰度为0.92%~1.16%,以菌藻类生源为主,有机质类型主要为Ⅱ型,有机质丰度高;普斯格组下段发育三角洲前缘、滨浅湖沙坝优质砂岩储层,砂体厚度为42.5~63m,砂地比为27%~47%,是一套分布较广的区域性储层,与普斯格组上段泥岩组成优质储盖组合;柯克亚周缘发育印支期、喜马拉雅期两期构造变形,古生界叠瓦冲断、强烈逆掩叠置,圈闭成排成带,喜马拉雅期进一步挤压抬升改造,局部复杂化,形成的叠瓦冲断带为勘探有利区。根据普斯格组天然气干燥系数分析,折算Ro为1.31%~1.42%,与下盘烃源岩成熟度相当,表明油气来自下盘逆掩叠置烃源岩,经历早油晚气的成藏过程,成藏具有“逆掩叠置下盘供烃、下生上储、断裂输导”的特点。综合分析认为该地区二叠系普斯格组圈闭成排成带分布,已发现圈闭9个,面积301km^(2),天然气资源量约为2930×10^(8)m^(3),凝析油资源量约为2×10^(8)t,具有较好的勘探前景。